Hi @Tom James
Do reply above help?
Yes, a user must have an Exchange Online license in order to access a shared mailbox. Shared mailboxes don’t require a separate license. However, if you want to enable In-Place Archive or put an In-Place Hold or a Litigation Hold on a shared mailbox, you must assign an Exchange Online Plan 1 with Exchange Online Archiving or Exchange Online Plan 2 license to the shared mailbox.
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